Size of the memory

Question

When we create types what will be the size of the memory? For example: Employee myAssistant = new Employee ();

Vulpes · Answer

Apart from the string type all the built-in types in C# require a fixed amount of memory. For example: int (4 bytes) double (8 bytes) decimal (16 bytes) bool (1 byte) and char (2 bytes). For user-defined types there is no maximum memory size as such - though the allocation of such objects would of course be limited by available memory. In practice the biggest types are generally arrays lists dictionaries and strings. If a type requires more than 85K bytes it is stored in a special area of the heap (the large object heap or LOH). In the normal heap when objects are deleted objects higher in memory are moved down to fill up the space and new objects are then allocated at the end. In contrast in the LOH memory is not condensed in this way when objects are deleted. When new large objects are allocated an attempt is first made to allocate them in one of the 'holes' left by previously deleted objects and if this proves impossible then they are then allocated at the end of the LOH. This can sometimes lead to a situation where an out of memory exception occurs even though there appears to be plenty of available memory remaining.

Maha · Answer

Thank you for your explanation.

Maha · Answer

For built-in types there is a maximum value for memory size. I wish to know is there any maximum value for user defined types?

Maha · Answer

Thank you for your explanation.

Vulpes · Answer

An instance of the Employee type will occupy the following memory: 1. The sum of the memory occupied by each of its fields. 2. Possibly some padding to ensure the fields are aligned on appropriate boundaries for the processor being used. 3 If Employee is a class overhead of 8 bytes (32 bit processor) or 16 bytes (64 bit processor). If Employee is a class then the memory will be allocated on the heap and the variable myAssistant will contain a reference (a type of pointer) to this memory. This reference will occupy 4 bytes on a 32 bit processor or 8 bytes on a 64-bit processor. If Employee is a struct then the memory may be allocated on the stack or the heap (depending on the circumstances) and the variable myAssistant will contain the actual struct instance not a reference to it.